In the semiconductor industry, thinning of a semiconductor wafer is proceeding so as to respond to thinning of package or high density packaging by the technique of stacking chips. Thinning is performed by so-called back-surface grinding of grinding a wafer surface in the side opposite the pattern-formed surface (circuit face). Usually, in conventional techniques of performing the back-surface grinding and conveyance while holding the wafer only by a backgrinding protective tape, thinning can be accomplished in practice only to a thickness of about 150 μm because of problems such that the wafer with the protective tape is warped after grinding or the thickness at the grinding is low in the uniformity. In order to solve these problems, polyethylene terephthalate (PET) having high rigidity and large thickness (from 100 to 200 μm) is used as the substrate of the backgrinding protective tape and thereby a semiconductor wafer having a thickness of about 50 μm can be produced.
Meanwhile, the thinned semiconductor wafer is cut into individual chips through a cutting step called dicing process. Particularly, in obtaining chips from a semiconductor wafer thinned to an extremely small thickness of 50 μm or less, a low yield in the dicing process becomes a problem. This is because in a normal method of dicing a semiconductor wafer thinned by back-surface grinding and laminated to a pressure-sensitive adhesive tape called dicing tape, chipping (edge chipping) is generated at the dicing of the semiconductor water in contact with the pressure-sensitive adhesive sheet and the yield greatly decreases.
In order to solve this problem at the dicing of the semiconductor wafer, Japanese Unexamined Patent Publications (Kokai) No. 5-335411, Kokai No. 2000-195826 and Kokai No. 2002-353170 disclose a method where a groove having a depth larger than the final finish thickness is previously provided by half-scribing in scribe lines (lines to be cut later, which are dividing individual semiconductor chips) on the circuit face before the back-surface grinding of the semiconductor wafer and by the subsequent back-surface grinding, the division into chips is performed at the same time with the grinding. In this method, the yield in the dicing process of an ultrathin wafer can be greatly improved. However, the adhesion of a die bonding tape to the ground face after the grinding, which is necessary mainly in the application to stacked IC and the like, is performed after the wafer is divided, therefore, only the die bonding tape must be separately diced and the productivity greatly decreases.
As another method capable of preventing chipping, Kokai No. 6-132432 discloses a method of back-surface grinding a semiconductor wafer laminated on a hard support by using a wax, and then dicing the wafer from the back surface (non-circuit face). In this method, chipping can be prevented according to the kind of wax material, however, the semiconductor wafer after dicing must be dipped in a solvent so as to remove the wax and this decreases the productivity of chip manufacturing.